/*
 * Copyright (C) 2016 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.graph;

import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.graph.GraphConstants.INNER_CAPACITY;
import static com.google.common.graph.GraphConstants.INNER_LOAD_FACTOR;

import com.google.common.collect.ImmutableMap;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;

/**
 * An implementation of {@link GraphConnections} for undirected graphs.
 *
 * @author James Sexton
 * @param <N> Node parameter type
 * @param <V> Value parameter type
 */
final class UndirectedGraphConnections<N, V> implements GraphConnections<N, V> {
    private final Map<N, V> adjacentNodeValues;

    private UndirectedGraphConnections(Map<N, V> adjacentNodeValues) {
        this.adjacentNodeValues = checkNotNull(adjacentNodeValues);
    }

    static <N, V> UndirectedGraphConnections<N, V> of() {
        return new UndirectedGraphConnections<N, V>(new HashMap<N, V>(INNER_CAPACITY, INNER_LOAD_FACTOR));
    }

    static <N, V> UndirectedGraphConnections<N, V> ofImmutable(Map<N, V> adjacentNodeValues) {
        return new UndirectedGraphConnections<N, V>(ImmutableMap.copyOf(adjacentNodeValues));
    }

    @Override
    public Set<N> adjacentNodes() {
        return Collections.unmodifiableSet(adjacentNodeValues.keySet());
    }

    @Override
    public Set<N> predecessors() {
        return adjacentNodes();
    }

    @Override
    public Set<N> successors() {
        return adjacentNodes();
    }

    @Override
    public V value(Object node) {
        return adjacentNodeValues.get(node);
    }

    @Override
    public void removePredecessor(Object node) {
        @SuppressWarnings("unused")
        V unused = removeSuccessor(node);
    }

    @Override
    public V removeSuccessor(Object node) {
        return adjacentNodeValues.remove(node);
    }

    @Override
    public void addPredecessor(N node, V value) {
        @SuppressWarnings("unused")
        V unused = addSuccessor(node, value);
    }

    @Override
    public V addSuccessor(N node, V value) {
        return adjacentNodeValues.put(node, value);
    }
}
